EML when temp is up

Hi, i have a bit of a problem if anyone can help. I have a 2006 td4 auto. We've owned the car for nearly 2 years. After about a month of owning the EML started coming on on longer journeys. Had the car plugged in multiple times and it said there was a fuel issue. Have changed high pressure pump. Low pressure pump and filter. And every sensor in between, all pipes are fine and not corroded and injectors are working as they should. This didnt work. We've now realised if we drive with the heater on so temp guage doesn't go above the quarter the car runs perfectly fine, my next job will be the thermostat unless anyone has any other suggestons.....Thanks

Do you happen to know the code? Have you seen the same code repeated?

Have you by chance checked the fuel rail pressure sensor wiring? These are a known weak point causing problems that there is an upgraded loom for. Might be screwing up the fuel pressure reading to the ECU when it expands at a certain temp.

You may find that putting in a better thermostat setup (also another known TD4 issue I believe) will cause the problem to occur more frequently because a good setup will want to keep it at a higher temperature than 1/4 on the gauge.